U.S. patent application number 10/039873 was filed with the patent office on 2003-07-03 for flexible device for ablation of biological tissue.
This patent application is currently assigned to AFX INC.. Invention is credited to Berube, Dany, Chapelon, Pierre-Antoine.
Application Number | 20030125730 10/039873 |
Document ID | / |
Family ID | 21907784 |
Filed Date | 2003-07-03 |
United States Patent
Application |
20030125730 |
Kind Code |
A1 |
Berube, Dany ; et
al. |
July 3, 2003 |
Flexible device for ablation of biological tissue
Abstract
An ablation system incorporating an enhanced deflectable distal
portion, is provided. The system includes an elongated tubular
member having a deflectable distal portion adapted to assume a
specific predetermined or predefined shape when deployed. The
predetermined shape allows for the creation of a desired uniform
energy emission pattern with respect to a target tissue, such that
energy may be directed toward the target tissue independent of an
approach orientation of the ablation system. The energy pattern
results in the creation of a desired tissue ablation. The ablation
system may further comprise a steering system which aides in
directing the distal portion toward a target tissue site. The
steering system may alternatively be incorporated into a separate
guiding catheter as part of the ablation system.
Inventors: |
Berube, Dany; (Milpitas,
CA) ; Chapelon, Pierre-Antoine; (Fremont,
CA) |
Correspondence
Address: |
AFX INC.
47929 FREMONT BLVD
FREMONT
CA
94538
US
|
Assignee: |
AFX INC.
47929 FREMONT BLVD.
FREMONT
CA
94538
|
Family ID: |
21907784 |
Appl. No.: |
10/039873 |
Filed: |
January 3, 2002 |
Current U.S.
Class: |
606/45 ; 606/13;
606/16; 606/32; 606/33; 606/41 |
Current CPC
Class: |
A61B 18/1492 20130101;
A61B 18/1815 20130101 |
Class at
Publication: |
606/45 ; 606/13;
606/16; 606/32; 606/41; 606/33 |
International
Class: |
A61B 018/04; A61B
018/18 |
Claims
What is claimed is:
1. A flexible ablation system for ablation of biological tissue at
a target tissue site, comprising: a handle portion; a tubular
member having proximal and distal portions and a longitudinal axis
which, at a point just proximal to the distal portion, defines an
azimuth angle with respect to the target tissue, the handle portion
operably attached to the proximal portion of the tubular member; at
least one ablation element operably disposed at the distal portion
of the tubular member, the at least one ablation element adapted to
emit ablative energy; and a means for deflecting the distal portion
of the tubular member, wherein the distal portion of the tubular
member is configured to be deflected to a predetermined shape
wherefrom a desired energy pattern is emitted which is
substantially independent of the azimuth angle.
2. The system of claim 1 further comprising a means for
directionally controlling ablative energy emitted from the at least
one ablation element.
3. The system of claim 2, wherein the means for directionally
controlling ablative energy is flexible, whereby the directionally
controlling means deflects as the distal portion of the tubular
member is deflected.
4. The system of claim 3, wherein the means for directionally
controlling the ablative energy allows for the emission of energy
in a radial pattern, substantially 180 degrees about the
longitudinal axis of the distal portion.
5. The system of claim 4, wherein the means for directionally
controlling the ablative energy comprises a shield device adapted
to be opaque to at least a portion of the ablative energy emitted,
whereby a portion of biological tissue adjacent to the distal
portion of the ablation system is shielded from the ablation
energy.
6. The system of claim 5, wherein the shield member reflects at
least a portion of the ablative energy in a direction toward the
target tissue site.
7. The system of claim 6, wherein the geometric surface of the
shield member along a longitudinal axis is substantially
planar.
8. The system of claim 6, wherein the geometric surface of the
shield member along a longitudinal axis comprises at least one
curved portion corresponding to a desired ablation pattern.
9. The system of claim 8, wherein the shield member is
substantially convex with respect to the longitudinal axis of the
ablation system, the ablative energy being longitudinally dispersed
across a target tissue site.
10. The system of claim 8, wherein the shield member is
substantially concave with respect to the longitudinal axis of the
ablation system, the ablative energy being longitudinally focused
upon a target tissue site.
11. The system of claim 1, wherein the at least one ablation
element is flexible, whereby the at least one ablation element
deflects as the distal portion of the tubular member is
deflected.
12. The system of claim 11, wherein the at least one ablation
element is an antenna adapted to emit electromagnetic energy.
13. The system of claim 12, wherein the antenna is one selected
from the group consisting of: a linear antenna, a helical antenna,
a monopole antenna, and a lossy transmission line.
14. The system of claim 11, wherein the at least one ablation
element is an electrode having the form of a helical spring.
15. The system of claim 1, wherein the ablative energy is one or
more energies selected from the group consisting of: microwave,
laser or other forms of light energy in both the visible and
non-visible range, radio frequency (RF), ultrasonic, cryogenic,
thermal, and chemical.
16. The system of claim 1, wherein the deflection means comprises
at least one pull wire operably attached to a distal end of the
distal portion of the tubular member and the handle portion.
17. The system of claim 16, wherein the distal portion of the
tubular member is generally linear, translation of the at least one
pull wire results in deflection of the distal portion between a
linear configuration and a deflected configuration.
17. The system of claim 16, wherein the distal portion of the
tubular member is preformed, translation of the at least one pull
wire results in deflection of the distal portion between a
preformed configuration and a linear configuration.
18. The system of claim 1, wherein the predetermined shape is
curvilinear.
19. The system of claim 1, wherein the predetermined shape is
substantially circular.
20. The system of claim 19, wherein the predetermined shape has a
radius of from about 0.5 cm. to about 5 cm.
21. The system of claim 15, further comprising a means for steering
the distal portion of the tubular member, the steering means
operably attached to the tubular member and the handle portion,
wherein operation of the steering means effects a change in the
azimuth angle.
23. The system of claim 16 further comprising a guiding member
having at least one lumen passing therethrough and including a
means for steering the distal portion of the tubular member, the
tubular member translatably disposed within a first of the at least
one lumen, wherein operation of the steering means effects a change
in the azimuth angle while the tubular member is free to translate
within the guiding member.
24. The system of claim 23, wherein the distal portion of the
tubular member is preformed having a curvature of a predetermined
radius, whereby the distal portion of the tubular member assumes
its preformed curvilinear shape as the tubular member translates
out the distal opening of the guiding member.
25. The system of claim 24, wherein the predetermined radius is
from about 1 cm. to about 5 cm.
26. The system of claim 23, wherein the deflection means comprises
a springy member which acts to manipulate the distal portion of the
elongated tubular member to the predetermined shape in response to
a change in external forces acting thereupon.
27. The system of claim 26, wherein the springy member is a
superelastic material.
28. The system of claim 18, wherein the distal portion of the
tubular member further comprises at least one prebend of a
predetermined angle located proximal to the at least one ablation
element, whereby the prebend cooperates with the distal opening of
the guiding member and further deflects the distal portion of the
tubular member as the tubular member translates out the distal
opening of the guiding member.
29. A method of ablating tissue, comprising the steps of: providing
an ablation system comprising a tubular member having a deflectable
distal portion, the distal portion comprising at least one ablation
element from which ablative energy is emitted, the distal portion
being configured to be deflected to a predetermined shape wherefrom
a relatively uniform energy pattern is emitted; advancing the
distal portion of the ablation system into a patient's body until
the distal portion is near a target tissue site; deflecting the
distal portion of the ablation catheter, the distal portion
assuming the predetermined shape; advancing the distal portion of
the ablation catheter until the distal portion is proximate the
target tissue; and applying ablative energy to the at least one
ablation element to ablate the target tissue proximate the distal
portion of the ablation catheter.
30. The method of claim 29, wherein the ablation of the target
tissue results in the formation of at least one lesion as part of a
desired lesion path.
31. The method of claim 29, wherein the ablation catheter further
comprises a steering means operably attached to the ablation
catheter proximal to the distal portion thereof and the method
further comprises the step of operating the steering means such
that the distal portion of the ablation catheter is moved from a
first position to a second position.
32. The method of claim 31, wherein the first position and the
second position overlap and the step of ablating results in the
creation of a long continuous deep lesion corresponding to the
first and second position.
33. A method for ablating a target tissue within a hollow body
organ, the steps comprising: providing an elongated tubular member
having a means for deflecting a distal end thereof, the distal end
including at least one ablation element, wherein operation of the
deflection means results in the creation of a desired energy
pattern about the distal end of the elongated tubular member;
advancing the distal end of the tubular member to a point where at
least a portion of the distal end is within the hollow body organ;
operating the deflection means to deflect at least a portion of the
distal end of the tubular member; positioning at least a portion of
the distal end of the tubular member proximate to the target
tissue, the longitudinal axis of the tubular member immediately
proximal to the distal portion thereof and the target tissue
defining an azimuth angle therebetween; ablating at least a portion
of the target tissue.
34. The method of claim 33, wherein the step of advancing the
distal end comprises the step of advancing the distal end of the
tubular member until the distal portion thereof is within the
hollow body organ.
35. The method of claim 33, wherein the step of operating the
deflection means results in the creation of a uniform energy
pattern about the distal portion of the elongated tubular member
such that the step of ablating occurs without respect to the
azimuth angle.
36. The method of claim 33, wherein the azimuth angle is from about
0.degree. to about 180.degree..
37. The method of claim 33, wherein the elongated tubular member
further comprises a steering means and the step of positioning
comprises the step of positioning at one of a plurality of
positions.
38. The method of claim 37, wherein the plurality of positions
define a continuous ablation path.
39. The method of claim 38, wherein the step of ablating results in
the formation of a long continuous deep lesion along the ablation
path.
40. An ablation system for ablating a hollow body organ,
comprising: an elongated tubular member having a means for
deflecting a distal portion thereof, the longitudinal axis of the
tubular member immediately proximal to the distal portion and the
surface of a target tissue defining an angle therebetween; and an
ablation device operably disposed at the distal end of the
elongated tubular member and including at least one ablation
element adapted to emit ablative energy therefrom, wherein
operation of the deflection means results in the creation of a
uniform energy pattern about the distal portion of the tubular
member, whereby ablation of a portion of the target tissue occurs
independent of the angle.
41. The system of claim 40 wherein deflection means comprises at
least one pull wire having a distal end fixedly attached to the
distal portion.
42. The system of claim 41, wherein the at least a portion of the
at least one pull wire is operably located external and adjacent to
the distal portion.
43. The system of claim 40, wherein the at least one ablation
element is an antenna adapted to emit electromagnetic energy
therefrom.
44. The system of claim 40, wherein the at least one ablation
element is an electrode.
45. The system of claim 40, wherein the ablative energy is one or
more energies selected from the group consisting of microwave,
laser or other forms of light energy in both the visible and
non-visible range, radio frequency (RF), ultrasonic, cryogenic,
thermal, and chemical.
46. A flexible ablation system, comprising: a tubular member having
proximal and distal portions and a longitudinal axis which, at a
point just proximal to the distal portion, defines an azimuth angle
with respect to the target tissue; and at least one ablation
element operably disposed at the distal portion of the tubular
member, the at least one ablation element adapted to emit ablative
energy; and a means for shaping the distal portion of the tubular
member, wherein a desired energy pattern is emitted from the shaped
distal portion, the energy pattern engaging a target tissue
independent of the azimuth angle.
47. The system of claim 46, wherein the at least one ablation
element is configured to emit ablative energy substantially
perpendicular to the longitudinal axis of the tubular member.
48. An ablation system for ablating biological tissue, comprising:
a tubular member having a distal portion and a longitudinal axis;
at least one ablation element operably disposed at the distal
portion of the tubular member and adapted to emit ablative energy
in a substantially lateral direction along the longitudinal axis of
the tubular member; and a means for deflecting at least the distal
portion of the tubular member, wherein upon deflection of at least
a portion of the distal portion of the tubular member, a relatively
uniform energy distribution is formed about the deflected
portion.
49. The system of claim 48, wherein the deflected portion is shaped
to follow the natural contour of the biological tissue.
50. The system of claim 49, wherein the surface of the biological
tissue is concave.
51. The system of claim 48, wherein the at least one ablation
element is adapted to emit unidirectional ablative energy.
52. The system of claim 49, wherein the biological tissue is the
isthmus between the inferior vena cava and the tricuspid valve.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] The present invention relates generally to catheter systems
used in diagnosis and treatment of various body tissues and, more
specifically, to ablation systems for ablating cardiac tissue in
the treatment of electrophysiological diseases.
[0003] 2. Description of the Related Art
[0004] As is well know, catheters provide medical professionals
access to various interior regions of the human body in a minimally
invasive manner. In such a way, catheters are tremendous medical
tools in support of diagnosis and treatment of different tissues of
the body. Catheters allow such professionals to place one or more
medical instruments, pharmacological agents or other matter at a
target tissue site. For example, in cardiac procedures in support
of diagnosis and treatment of atrial fibrillation, catheters
provide access to various chambers of the heart, carrying ablation
devices which translate therein to such sites for ablation of
specific cardiac tissue associated with atrial fibrillation.
[0005] Ablation of tissue, cardiac tissue for example, is typically
directly related to the orientation of the ablation element, from
which energy sufficient to ablate biological tissue is emitted,
with respect to a target tissue site. For such procedures, precise
control of the ablation device is desirable to ensure proper
placement of the ablation element utilized in creation of one or
more desired lesions. As an electrophysiologist, or other medical
professional, manipulates the proximal end of the catheter system,
the distal end of the catheter must be responsive to such movement
in a very predetermined, smooth-flowing and proportional way.
[0006] Additionally, the orientation of the ablation device, from
which ablative energy is emitted and directed toward the target
tissue, differs with the modality utilized for the procedure. For
example, with tip electrode RF based devices, the tip must be
properly placed in direct contact with the target tissue. For
creation of numerous intermediate lesions along a desired lesion
path, the tip electrode must be moved across the target tissue
surface in a controlled fashion, which is often difficult due to
inconsistencies of the tissue surface. Under certain conditions,
the tip may act to impede movement across the surface of the target
tissue, causing the tip to erratically jump or skip across the
tissue in an undesirable way.
[0007] For example, for the treatment of atrial flutter, it is
often desirable to ablate the isthmus which lies between the
inferior vena cava and the tricuspid valve. The contour of this
tissue, while generally curvilinear, is irregular and inconsistent,
comprising various peaks and valleys, which differ from individual
to individual. Ablating tissue in this region often requires the
precise and controlled placement of the distal tip of the ablation
device. Because of the curvilinear nature of the isthmus, it has
been found to be difficult to lay down a straight long linear
ablation element to ablate this area. This task is complicated by
the fact that the steering or guiding system of the ablation system
typically directly impacts the approach and orientation of the tip
upon the tissue, which further impairs the ability of the system to
transmit sufficient ablative energy for proper tissue ablation.
Furthermore, due to the desired depth of the ablation required at
this location, proper placement of the ablation device is critical
to the creation of a desired long continuous deep lesion
therein.
[0008] Proper placement of an ablation device is also exasperated
by the fact that some ablative energy technologies require energy
transmission conduits which are bulky, or otherwise constructed
from materials less flexible, making the distal portion of the
catheter difficult to properly position. For example, distal
portions of optical fiber or microwave based ablation systems, or
catheter systems comprising an endoscopic device, may be more
difficult to maneuver due to the lack of flexibility in the
transmission mediums utilized therein. As should be readily
apparent, when the distal portion of an ablation catheter system is
not properly positioned, ablative energy is not properly directed
and applied to the target tissue, resulting in poor lesion
formation. It is therefore essential that the ablative device be
able to be manipulated and sufficiently controlled to be properly
positioned to transfer the requisite energy to ablate biological
tissue and create a desired lesion therein.
SUMMARY OF THE INVENTION
[0009] Accordingly, it is a general object of the present invention
to provide an ablation system which resolves the above-identified
problems. Another object of the present invention is to provide an
ablation system which ensures proper placement of an ablation
device upon a target tissue to be ablated. Yet another object of
the present invention is to provide an ablation system
incorporating a deflectable ablative device which can emit a
relatively uniform energy pattern therefrom. Another object of the
present invention is to provide an ablation system to ablate
tissue, forming a lesion therein which is substantially independent
of an azimuth or approach angle. Still another object of the
present invention is to provide an ablation system to easily and
effectively ablate the isthmus between the inferior vena cava and
the tricuspid valve without the need for a precise deflection
system. Yet another object of the present invention is to provide a
catheter system which ensures proper placement of an ablation
device proximate a target tissue site during creation of a long
continuous lesion.
[0010] These and other objects are achieved through systems
disclosed herein. More specifically, a system for ablating a
selected portion of biological tissue at a target tissue site is
provided. The system is particularly suitable to ablate cardiac
tissue, as well as other soft tissues of the body, and includes a
tubular member having a distal end including an ablative device
which, in turn, includes one or more ablation elements adapted to
emit ablative energy therefrom, and a steering system operably
attached to a proximal section. The distal end of the tubular
member is configured to be deflected into a predetermined geometric
shape wherefrom a relatively uniform energy pattern is emitted,
such that tissue ablation can occur substantially independent from
an approach angle defined between the tubular member and the target
tissue surface. In this way, for example, with a substantially
side-firing ablation device one could bend or otherwise deflect the
ablation device into a specific shape to obtain a uniform energy
distribution about the distal end of the ablation device.
[0011] In one embodiment, the ablation device includes at least one
ablation element adapted to emit ablative energy therefrom. The
ablation device is configured to engage tissue from one of many
approach angles while maintaining proper ablative energy transfer
to the tissue resulting in tissue ablation and the creation of one
or more desired lesions.
[0012] In another embodiment, the ablation device includes at least
one flexible ablation element adapted to emit ablative energy
therefrom. The at least one ablation element is configured to
deflect along with the tubular member. Alternatively, the ablation
device may include at least one ablation element having a geometric
configuration which allows deflection of the distal end of the
ablation device.
[0013] In still another embodiment, the ablation device may also
include a shielding means adapted to be opaque with respect to the
corresponding ablative energy utilized, protecting tissues
surrounding a target tissue site from the ablative energy.
Additionally, the shielding means may be configured to reflect at
least a portion of the ablative energy toward the target tissue
site to facilitate or encourage tissue ablation and lesion
formation.
[0014] In still another embodiment, the tubular member of the
ablation device translates within a tubular guiding member, the
distal portion of the ablation device is adapted to include a
preformed shape. As the ablation device emerges from the distal
opening of the guiding member, the distal end assumes its preformed
curvilinear shape. The preformed shape may be selected to
facilitate the emission of a uniform energy pattern therefrom.
[0015] In another embodiment, the ablation device is a catheter
system wherein the tubular member is elongated to facilitate entry
into a patient's vascular system and advancement to a target tissue
site, a cardiac muscle site for example.
[0016] The ablative energy is preferably electromagnetic energy in
the microwave range. However, other suitable tissue ablation
energies include, but are not limited to, cryogenic, ultrasonic,
laser, chemical and radiofrequency.
[0017] In yet another embodiment, the ablation device is a
microwave antenna assembly which includes an antenna configured to
emit microwave ablative energy. The ablation device may also
include a shielding means coupled to the antenna assembly. The
shielding means may be adapted to substantially shield a
surrounding area of the antenna from the electromagnetic field
radially generated therefrom while permitting a majority of the
field to be directed generally in a predetermined direction toward
the target tissue site. Alternatively, the shielding means, in
another embodiment, may be adapted to absorb the electromagnetic
energy transmitted therefrom protecting surrounding tissues. The
ablation device may further include an insulator which functions to
hold the shielding means and antenna in fixed relationship with
respect to each other and a target tissue site, further controlling
the ablative characteristics of the ablation device.
[0018] In yet another embodiment, the steering system is part of an
elongated guiding member having at least one lumen passing
therethrough, the tubular member of the catheter translating
therein.
[0019] In another aspect of the present invention, a method for
treatment of a Heart includes entering the ablative device into a
patient's vasculature; guiding the distal end of the ablation
device into a chamber of the patient's heart; manipulating the
ablation device until the distal end is proximate a target tissue
site; applying ablative energy from an energy source to the
ablation device.
[0020] In one embodiment, the manipulating is performed by
incrementally advancing the ablative device along a plurality of
positions along an ablation path to produce a substantially
continuous lesion.
[0021] In another embodiment, the step of manipulating is performed
by incrementally sliding, or otherwise moving, the ablative device
along a predefined ablation path to produce a long and
substantially continuous lesion.
[0022] In yet another embodiment, the step of sliding includes the
step of positioning the ablative device in an overlapping
arrangement with respect to prior ablation sites along the ablation
path.
[0023] Other objects and attainments together with a fuller
understanding of the invention will become apparent and appreciated
by referring to the following description and claims taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1A is a side view of an ablation system.
[0025] FIG. 1B is a side view of an ablation system including a
flexible distal portion in accordance with the present
invention.
[0026] FIG. 2A-E are side views of an ablation system being
deployed, in accordance with the present invention.
[0027] FIGS. 3A-C are side views of an alternative embodiment of an
ablation system, in accordance with the present invention.
[0028] FIG. 4A is a side view of a first embodiment of an ablation
system in accordance with the present invention.
[0029] FIG. 4B is an end view of the ablation system of FIG.
4A.
[0030] FIG. 5A is a side view of another embodiment of an ablation
system in accordance with the present invention.
[0031] FIG. 5B is an end view of the ablation system of FIG.
4A.
[0032] FIG. 6A is a side view of the ablation system of FIG. 5A
shown with the distal end deflected to a first position.
[0033] FIG. 6B is a side view of an ablation system incorporating
an alternative ablation device, in accordance with the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0034] While the present invention will be described with reference
to a few specific embodiments, the description is illustrative of
the invention and is not to be construed as limiting the invention.
Various modifications to the present invention can be made to the
preferred embodiments by those skilled in the art without departing
from the true spirit and scope of the invention as defined by the
appended claims.
[0035] Turning to FIG. 1A, a catheter 20 known in the art will be
discussed. More specifically, FIG. 1A depicts catheter 20 advanced
from a point proximate to the femoral vein (not shown), through the
inferior vena cava 14 (IVC), and into the right atrium 16, a distal
tip 26 of catheter 20 engaging cardiac tissue 10, between the IVC
14 and tricuspid valve 12. For purposes of clarity, the depiction
of the cardiac structure has been simplified.
[0036] The catheter 20 comprises a long tubular member 22 having a
proximal portion (not shown) and distal portion 24, the proximal
portion operably attached to a handle portion (not shown). The
distal portion 24 includes, or otherwise incorporates, an ablation
device 30 including one or more ablation elements. The one or more
ablation elements are arranged and configured to emit ablative
energy in a direction generally away from an emission surface of
the catheter 20 body, a portion of the radiating energy pattern
generally designated by the arrows E and the emission surface
corresponding to the outer catheter surface from which the energy
is emitted, directly or indirectly, with respect to catheter
20.
[0037] As should be readily apparent, the emission surface may
comprise the surface of one or more ablative elements embedded
thereon, such as one or more electrodes adapted to contact target
tissue and emit thermally conductive ablative energy.
Alternatively, one or more ablative elements may be encased within
the ablation device itself, the catheter structure allowing a
substantial portion of the ablative energy to pass therethrough and
engage target tissue. Such a system has the additional advantage,
especially when the material within which the ablative elements are
encased absorbs substantially none of the ablative energy which
passes therethrough, of not charring or adhering to the target
tissue, or causing other tissue damage generally associated with
thermal conduction based systems.
[0038] The steering system of catheter 20 typically comprises at
least one pull wire operably attached to a control means as part of
the handle portion (not shown) and the distal portion 24 at an
attachment point A. Operation of the control means results in the
deflection of distal portion 24 of catheter 20. Since the
attachment point A is close to the distal end 26 of distal portion
24 it is often difficult for an operator, an electrophysiologist
for example, to manipulate the distal portion 24 in such a way as
to position the emitting surface substantially proximal and
parallel to cardiac tissue 10 in order to create a desired lesion
therein. As depicted in FIG. 1A, with an improperly positioned
distal portion, a substantial portion of the ablative energy fails
to effectively engage tissue 10. Rather, the energy E.sub.1 is
absorbed in the blood.
[0039] As further depicted in FIG. 1A, when a portion of distal end
26 engages tissue 10, an approach angle .alpha. is defined between
a longitudinal axis line L of catheter 20 which passes through
attachment point A and the surface of tissue 10. Certain catheter
systems may have distal energy delivery or ablation elements which
are adapted to deliver an energy pattern from the distal end of the
system toward a target tissue, distal end 26 toward tissue 10 for
example, as depicted by arrows E.sub.2. As should be readily
understood, when catheter 20 is positioned as shown in FIG. 1A,
distal end 26 is not effectively placed perpendicularly in contact
with tissue 10. Thus, tip-firing energy E.sub.2, like energy
E.sub.1, is not effectively transmitted to tissue 10, resulting in
poor ablation formation therein. Therefore, when approach angle
.alpha. is about 0.degree., energy E.sub.1 is most effectively
transmitted to tissue 10. Conversely, when approach angle .alpha.
is about 90.degree., energy E.sub.1 is most effectively transmitted
to tissue 10.
[0040] It is important to note that energy patterns E.sub.1 and
E.sub.2 are generic in the sense that they do not depict energy
patterns of ablation systems which require direct contact with the
target tissue. However, as is discussed in more detail below, use
of such systems is enhanced through the addition of structures and
methods in accordance with the present invention. For example, if
distal tip 26 of catheter 20 included an electrode which required
direct contact with target tissue 10, such a device would be
difficult to maneuver and manipulate in such a way as to create
numerous intermediate lesions as part of a long continuous lesion,
especially during a beating heart procedure.
[0041] Now turning also to FIG. 1B, a catheter 100 in accordance
with the present invention is shown. As depicted in FIG. 1A with
respect to catheter 20, catheter 100 is shown passing through the
inferior vena cava 14, the distal end 124 entering the right atrium
16. Catheter 100 comprises an elongated tubular body member 110
which leads to a distal portion 124, and finally a distal end 126.
Distal portion 124 comprises an ablation device 130 (not shown)
including one or more ablation elements 136 (not shown) adapted to
emit ablative energy therefrom toward a target tissue site.
[0042] Catheter 100 further incorporates a steering system 102
having a distal attachment point A located proximal to distal
portion 124. As is discussed in greater detail below, once distal
portion 124 is within the right atrium, tension is applied to a
pull wire 104 which acts to deflect portion 124 substantially as
shown. Therefore, as should be readily apparent from FIG. 1B, as
the catheter 100 is deflected by steering system 102 from an
initial position (shown in dashed line), with point A moving in a
direction indicated by arrow D, the portion of catheter 100
distally located from point A is directed toward at least a portion
of target tissue 10. Such a configuration enables the distal
portion 124 of catheter 100 to be placed proximal to target tissue
10, allowing the emitted energy pattern E adjacent the point of
contact to effectively impact upon target tissue 10, ensuring
proper lesion formation at that location.
[0043] As shown, when the distal portion 124 engages tissue 10,
angle .alpha..sub.1 is defined by the longitudinal axis line
L.sub.1 of catheter 100 which passes through attachment point A and
tissue 10. The overall flexibility of distal portion 124 is
sufficiently greater than tubular member 110, such that translation
of pull wire 104 results in the deflection of portion 124 with
respect to tubular member 110, which substantially retains its
form.
[0044] Thus, it should be apparent that such a catheter system 100
is much less dependent on the approach angle .alpha. for proper
lesion formation adjacent the point of contact between catheter 100
and tissue 10, unlike catheter 20 discussed above. Moreover, the
distal portion 124 can be preformed or deflected to take on a
curvilinear shape allowing ablation systems which require direct
contact with the target tissue to be more easily moved in a
controlled manner about the surface of the target tissue. For
example, if one or more electrodes are placed along the distal
portion 124, one or more of the electrodes may be energized at any
given time during movement of distal portion 124 about tissue 10.
Such a system offers better control and performance with respect to
tip electrode systems which rely on moving the tip itself across
the surface of the tissue.
[0045] As will be discussed in more detail below, steering system
102 may be incorporated into a separate guiding catheter (not
shown), such that the ablation catheter, having an ablation device,
can translate therein. It should also be noted that while the
ablation device may be described as being deflected through
operation of pull wire 104, this does not necessary mean the
orientation of the ablation device is straight or linear. For
example, the ablation device may be curved to address the natural
curvature of an internal organ or to assist in its proper
placement, the ablation device directed to the target tissue
through the use of a guiding catheter configured to restrict the
ablation device to an orientation similar to the guiding catheter
until the ablation device emerges and assumes its predetermined
form.
[0046] The ablation device may also incorporate a shielding means
adapted to be opaque with respect to the corresponding ablative
energy utilized, protecting surrounding tissues from the ablative
energy. Additionally, the shielding device may be adapted to
reflect at least a portion of ablation energy toward the target
tissue site.
[0047] Steering system 102 may be any suitable steering system able
to properly deflect catheter 100 to achieve the desired ablations
described herein. Such steering systems are disclosed in commonly
owned and co-pending U.S. Patent Application entitled, "Catheter
Having Improved Steering," filed concurrently with the present
application and hereby incorporated herein, in its entirety.
[0048] Additionally, it should be noted that while the pull wire
104 is shown traveling outside the catheter 100 structure,
proximate to distal portion 124, the distal portion 124 may
comprise a lumen (not shown) ending near the distal tip through
which the pull wire 104 can translate. The lumen would be adapted
to minimize frictional forces between itself and pull wire 104 as
well as provide attachment point DA at a distal end of the lumen
near tip 126. In this way, all components of catheter 100 may be
encased within the catheter itself.
[0049] In operation, catheter 100 is steered, or otherwise
directed, through the operation of steering system 102. Since the
steering system 102 is operably attached at point SA along catheter
100, the catheter 100 structure distal to point SA remains
substantially unaffected by catheter steering. As is discussed in
greater detail below, with reference momentarily to FIG. 4A, once
the distal portion 124 is directed toward a target area within the
patient, within the right atrium for example, distal portion 124 is
further deflected through operation of pull wire 104.
[0050] Now turning to FIGS. 2A-2E, the operation of catheter system
100 can be more readily understood. While FIGS. 2A-2E depict the
ablation, or otherwise medical treatment, of the isthmus between
the inferior vena cava (IVC) 14 and tricuspid valve 12, it should
be apparent that such a system 100 can be utilized in other areas
of the body or in association with other bodily organs, such as the
bladder or stomach. As shown in FIG. 2A, catheter 100 is depicted
advancing percutaneously from a point proximal to the IVC 14, the
femoral vein for example, toward the target tissue site.
[0051] Now referring specifically to FIG. 2B, as the distal portion
124 of catheter 100 enters the right atrium 16, the steering system
102 acts to deflect distal portion 124 and direct distal tip 126 in
a direction generally toward the tricuspid valve 12. As is
depicted, and as should be readily understood, once the distal
portion 124 is within the right atrium, the catheter 100 is
typically no longer advanced, however, distal portion 124 is
continually deflected by operation of the steering system 102, as
described in greater detail above. Continued operation of the
steering system 102 results in further deflection of distal portion
124 with respect to the catheter member 110, attachment point A
moving generally in a direction noted by arrow M1.
[0052] With reference also to FIG. 2C, once the distal portion 124
lies within the atrium 16, the distal portion 124 is deflected
through translation of the pull wire 104, as described in greater
detail above. Once the distal portion 124 is deflected the desired
predetermined amount, approximately 180.degree. as shown for
illustration purposes only, the distal portion is further directed
towards target tissue through continued operation of steering means
102, as depicted in FIG. 2D. The distal portion 124 is steered, or
otherwise further manipulated, until the a portion of the distal
portion 124 is positioned proximate the target tissue 10, indicated
by position P1. As discussed above, irregardless of the approach
angle .alpha., with the distal portion 124 positioned as shown,
ablative energy impinges upon target tissue 10 to create a first
ablation and corresponding lesion at position P1.
[0053] Once the first ablation is complete, further operation of
steering means 102 results in the distal portion 124 moving in a
direction generally depicted as M2 along tissue 10 until a second
position is reached, indicated by position P2 as shown in FIG. 2E.
Additionally, once the ablation at position P2 is complete, the
distal portion 124 is further advanced as described above until a
position P3 is reached.
[0054] Now with reference to FIGS. 3A-3C, another embodiment of an
exemplary catheter system will be discussed. As depicted, catheter
system 200 comprises a guiding catheter 201 having at least one
lumen passing therethrough, and a steering system 202 operably
attaching to guiding catheter 201 generally at the attachment point
SA. Catheter system 200 further comprises an ablation catheter 204
which translates through the at least one lumen of the guiding
catheter 201. Ablation catheter 204 comprises a deflection means
for deflecting the distal portion 224 thereof. The deflection means
may be any suitable means, such as the deflection means described
above with reference to catheter system 100.
[0055] Preferably, the deflection means comprises a preformed or
preshaped support member 250 encased within a portion of distal
portion 224. Member 250, when no external forces are acting upon
distal portion 224, acts to deflect distal portion 224 to its
preformed or preshaped orientation. The flexibility of member 250
is somewhat less than that of guiding catheter 201, such that as
the distal portion 224 exits the distal opening of catheter 201,
distal portion 224 takes on the preformed shape of member 250, as
is discussed in more detail below. Support member 250 may be formed
having any suitable cross-sectional geometry including, but not
limited to, circular, square, elliptical, or rectangular. For
example, the cross-sectional geometry may be in the form of a
rectangle limiting its deflection to the geometric plane passing
through the longitudinal axis of the ablation catheter 204 during
deflection of distal portion 224. In this way the distal portion
224 may be more precisely placed upon target tissue.
[0056] As with catheter system 100 discussed above, operation of
catheter system 200 requires introduction of the catheter system
into a patient's body, through the vasculature for example, and
advanced until a distal portion is proximate target tissue to be
ablated. Once the distal portion is in place, the catheter system
200 can be further manipulated to allow for ablation of the target
tissue and formation of one or more desired lesions.
[0057] As shown in FIG. 3A, guiding catheter 201 of catheter system
200 is entered into the patient's vasculature, proximate to the
femoral vein for example, and advanced into the IVC 14 until a
distal portion 203 of catheter 201 is within the right atrium 16,
substantially as shown. Once the guiding catheter 201 is properly
placed, the ablation catheter 204 is translated through the at
least one lumen of catheter 201 in a direction indicated by arrow M
until a distal end of catheter 204 is positioned adjacent the
distal opening of guiding catheter 201, as generally depicted by
FIG. 3A.
[0058] With reference also to FIG. 3B, once the guiding catheter
201 is properly positioned, the ablation catheter 204 is further
advanced by operation of the advancement means by the user allowing
the distal portion 224 to exit the distal opening of the guiding
catheter 201. As depicted specifically in FIG. 3B, as the distal
portion 204 exits guiding catheter 201, the support member 250 acts
to deflect the distal portion 204 into a predetermined shape, as
discussed above. With reference also to FIG. 3C, as the ablation
catheter 204 is further advanced, the distal portion 224 further
takes on the predetermined shape of support member 250 until the
final shape is achieved. For illustrative purposes only, FIG. 3C
depicts the distal portion 224 of ablation catheter 204 in a
semi-circular shape. It should be apparent that other shapes can be
selected, these shapes being directly based on the target tissue
selected.
[0059] Once the distal portion 224 takes on its desired
predetermined shape, the ablation catheter 204 is further advanced
until at least a portion of distal portion 224 engages or is
otherwise proximate to the target tissue. An exemplary position is
shown in dashed line in FIG. 3C, distal portion 224 engages target
tissue 10 generally at the position indicated by P1. The steering
system 201 of guiding catheter 201 is further manipulated by the
User to further move distal portion 224 across target tissue 10,
creating intermediate lesions as part of a desired lesion path as
further discussed above with respect to catheter system 100.
[0060] Now turning to FIGS. 4A and 4B, an exemplary catheter system
100A having a deflectable distal portion in accordance with the
present invention will be discussed in greater detail. As stated
above with respect to catheter 100, generally catheter 100A
comprises elongated tubular member 110 having at least one lumen
passing therethrough. The tubular member 110 ends in distal portion
124. As shown, distal portion 124 includes ablation device 130
comprising ablation element 136.
[0061] In the embodiment of FIGS. 4A and 4B, ablation element 136
is a flexible antenna encased in an insulating material 134 adapted
to emit electromagnetic energy radially about its structure over
substantially its entire length, a portion of the radiated energy
pattern generally depicted by arrows E. Insulating material 134
acts to hold ablation element 132 a fixed distance from the target
tissue, tissue 10 for example, when the distal portion 124 contacts
the tissue as depicted in FIGS. 2A and 2B. For the ablation device
depicted, the insulator is a low-loss dielectric material able to
transmit a substantial portion of ablative energy therethrough.
Such materials may include, but are not limited to, TEFLON.RTM.,
silicone, polyethylene, polyimide, or other materials having
similar properties.
[0062] Ablation element 136 is coupled to a transmission medium
adapted for transmission of ablative energy from an energy source,
a microwave generator for example. The transmission medium may
comprise, for illustration purposes only, a center conductor which
is electrically coupled to a proximal end of ablation element 136,
an outer conductor and an insulating material therebetween. For
example, the transmission medium may be a coaxial cable adapted to
transmit energy therethrough to ablation element 136 at
predetermined power levels sufficient for ablating the target
tissue. Additionally, for illustration purposes only, other
exemplar modalities may include one or more optical fibers as part
of a laser ablation system, metallic wires or coaxial cable for an
ultrasound or RF ablation system, and tubular members having
passages therethrough for fluid or gas agents utilized by cryogenic
ablation systems.
[0063] It should be noted that the efficiency of ablation device
130 is related to, among other things, the ability of the
transmission medium to effectively transmit energy from the energy
source to ablation element 136. Therefore, ablation device 130 may
further comprise elements which maximize the efficiency of the
ablation system. For example, these elements may comprises one or
more passive components which interface to one or more elements of
the ablation system, comprising the energy source, transmission
medium and ablation device, acting to match the impedance
characteristics of, or otherwise tune, the ablation system
itself.
[0064] While ablation element 136 is depicted as a linear antenna
structure, any suitable structure can be used including, but not
limited to, a helical antenna, an isolated monopole antenna, a
lossy transmission line, or an exposed monopole antenna. The
ablation element 136 can be formed from any suitable material
including, but not limited to, spring steel, beryllium copper, or
silver-plated copper. The diameter of element 136 may be from about
0.005 to about 0.030 inches, and more preferably from about 0.013
to about 0.020 inches.
[0065] As shown, catheter 100A also includes pull wire 104 which
has distal and proximal ends, the distal end operably attached to
the handle portion (not shown) and the proximal end fixedly
attached to the catheter 100A at or near a distal tip 126,
designated as attachment point DA. The pull wire 104 exits the
tubular member 110 at or near the distal portion 124 through
opening 106 and travels along the exterior of member 110 to the
attachment point DA, as discussed immediately above.
[0066] While FIGS. 4 and 5 depict pull wire 104 loosely placed
within catheter 100, it should be apparent that pull wire 104 could
be enclosed within a separate tubular member 104A (not shown).
Member 104A would preferably run the length of catheter 100, the
proximal end fixedly attached to the handle portion (not shown) and
the distal end fixedly attached to catheter 100 structure.
Alternatively, member 104A could be part of the outer catheter 100
structure, fixedly attached to and integral to the structure along
the entire length of catheter 100. In this way, deflection forces
associated with distal portion 124 can be transmitted directly to
the handle portion, preventing undesirable deflection of catheter
100 and any tissue damage related thereto.
[0067] Distal portion 124 may optionally comprise a flexible
support member 150. Support member 150 runs substantially the
length of distal portion 124, with a proximal end of member 150
fixedly attached to catheter 100. Support member 150 preferably has
a rectangular cross-section encouraging deflecting of the distal
portion 124 along one plane. Support member 150 also acts to define
a minimum radius of curvature to ensure consistent deflection of
distal portion 124 along its length.
[0068] With reference now to FIGS. 5A and 5B, another catheter
system 100B shall be discussed. As depicted, the catheter system
100B is similar to system 100A except for distal portion 124.
Distal portion 124 of catheter 100B further comprises a shielding
means 152 adapted to shield surrounding tissue from ablative energy
emitted therefrom. As discussed above, shielding means 152 may act
to absorb ablative energy, microwave energy in this specific case,
or reflect and redirect the ablative energy toward the target
tissue to enhance ablation, reflection of the energy being a
function of the construction material of shielding means 152 and
redirection of the energy being a function of the geometric shape
of shielding means 152. To facilitate absorption of the microwave
energy, shielding means 152 may be formed from any suitable
microwave absorption material with high loss tangent, such as a
polymer filled with metallic powder for example. The geometric
structure of shielding means 152 may define the resulting energy
reflections to more precisely direct ablative energy toward target
tissue.
[0069] With reference to FIGS. 5A and 5B, shielding means 152 acts
to reflect at least a portion of the energy emitted by ablation
element 136 toward target tissue, tissue 10 for example, resulting
in more efficient ablation of the tissue. Furthermore, while
shielding means 152 is shown having a curvilinear geometric shape,
shielding means 152 may also be substantially planar in
construction, formed from metallic foil for example. Alternatively,
shielding means 152 may be constructed from a metallic wire mesh of
copper, the wire mesh having wire spacing sufficient to prohibit
passage of electromagnetic energy therethrough.
[0070] With reference now to FIGS. 6A and 6B, catheter systems 100
having differing ablation devices 130 will be discussed. With
specific reference to FIG. 6A, a catheter 100B is depicted having
distal portion 124 comprising ablation device 130 similar to that
depicted in FIGS. 5A and 5B. As shown, distal portion 124 is
deflected to a first position through translation of pull wire 104.
Once deflected, the ablation device 130 of catheter 100B emits an
ablative energy pattern as depicted by area E.sub.1. It should be
understood, as with other depictions described herein, the energy
pattern E.sub.1 may be depicted in a planar view, such as in FIG.
6A, however, the ablative energy emitted has three-dimensional
characteristics.
[0071] As discussed above, with the distal portion 124 deflected
and the ablation device emitting energy as depicted by pattern
E.sub.1, the angle of approach .alpha. of catheter 100B becomes
less significant. As described above, the longitudinal axis L of
catheter member 110, which passes through attachment point A
generally defines an attack angle .alpha. with respect to the
target tissue, tissue 10 for example.
[0072] This advantage is more clearly understood when considering
the distal portion engaging tissue 10A, the surface of tissue 10A
shown in dashed line. Here, the approach angle .alpha..sub.A, as
defined in a similar fashion as immediately above. As depicted by
the representative ablative energy pattern E.sub.1, an equivalent
amount of ablative energy is directed toward the target tissue 10,
10A, irregardless of the approach angle .alpha., .alpha..sub.A,
such that a desire ablation of the target tissue is performed. As
clearly shown in FIG. 6A, ablation of tissue 10 is not directly
dependent on the approach angle .alpha., .alpha..sub.A.
[0073] Further translation of pull wire 104 results in further
deflection of distal portion 124 to a second position shown in
dashed line. With the distal portion 124 deflected to the second
position a corresponding energy pattern E.sub.2 is produced. The
first and second position are exemplary positions depicting energy
dispersion from between approximately 180.degree. to about
270.degree.. It should be understood, however, that energy
dispersion ranges could vary from approximately 0.degree. to about
270.degree. with reference to the proximal end of portion 124,
depending on the needs of the user, a surgeon for example.
Additionally, it should be noted that while the ablation device 130
has been described as having a substantially circular
configuration, other configurations are contemplated within the
scope of the present invention to allow the User to ablate tissues
of differing geometries.
[0074] While the ablation device 130 of the catheter 100B
embodiment comprises support member 150, the shielding device 152
may be adapted to control the geometry of deflection with respect
to the distal portion 124. Additionally, as stated above, the
shielding means 152 may be configured such that the flexibility
changes along its longitudinal axis resulting in different
geometric configurations when distal portion 124 is deflected.
[0075] Now turning to FIG. 6B, another catheter 100 incorporating
an alternative ablation device is shown. Catheter 100C has a distal
portion 124 including an ablation device comprising at least one
radio frequency (RF) electrode 136A-E operably controlled by the
User through controlling means 140. The electrodes 136A-E of
ablation device 130 define an energy pattern depicted by E, shown
in dashed line. Controlling means 140 controls the application of
energy to the electrodes 136A-E, either alone, as a group of one or
more, or the entire group. For example, controlling means 140 of
catheter 100C may comprise one or more electrically conductive
wires operably connected to electrodes 136A-E and the handle
portion (not shown). The User would apply ablative energy to target
tissue through the direction of energy through one or more
electrodes 136A-E via controlling means 140.
[0076] It is important to note that the depiction of energy
dispersions discussed herein do not take into account the
efficiency of the different modalities disclosed herein. The energy
patterns described herein are for discussion purposed only. It
should be clear from the discussion herein that the energy emitted
from the ablation element(s) will impact target tissue in an
equivalent manner, without respect to an approach angle .alpha. as
defined herein.
[0077] Note that the ablation device 130 of distal portion 124 of
catheter 100C, may comprise more or less RF electrodes further
defining an appropriate energy pattern E. Furthermore, the RF
electrodes 136A-E may be in the form of a coiled spring such that
the RF electrodes themselves may individually deflect as the distal
portion 124 deflects. While the RF electrodes are shown in a
spaced-apart relationship with respect to each other, electrodes
136A-E may be positioned in close proximity with respect to each
other, further defining energy dispersion. Additionally, each RF
electrode 136A-E may be controlled separately through control means
140, further controlling or defining the energy dispersion area.
The electrodes 136A-E may be semi-circular defining an energy
pattern which is directed 180.degree. about the longitudinal axis
of the device, essentially defining a side-firing device which,
when the distal portion is deflected, can transform partially or
totally into a distal firing device.
[0078] While the above procedure is described in terms of three
lesions, the actual number of overlapping lesions is a function of
the ablative energy utilized and the configuration of distal
portion 124, comprising ablative device 130. For example, the
length of any intermediate lesion created is a direct function of
the dimensional characteristics of the ablation device utilized.
Therefore, the desired resultant long continuous lesion may
comprise the creation of fewer or greater intermediate lesions than
described above.
[0079] As discussed in more detail above, ablation device 130 may
also include an energy shielding means adapted to be opaque to the
ablative energy utilized, such that, tissue adjacent to target
tissue 10, for example, is protected from the ablative energy.
Furthermore, is should be noted that the energy shielding means can
be further adapted to reflect the ablative energy in a
predetermined and desirable fashion as to focus the ablative energy
at a desired region of the target tissue 10, whereby the lesion
characteristics can be better controlled.
[0080] For example, considering the ablative element of FIGS. 5A
& 5B, the shielding means may be formed to reflect and direct
microwave energy in a relatively thin line along the longitudinal
axis of the antenna, resulting in the desired formation of a
relatively thin long intermediate lesion. Alternatively, the
shielding means of a cryo based system may be constructed from
thermal isolating material, the shielding means 152 axially
surrounding a substantial portion of ablative device 130 leaving
only a relatively thin opening along the longitudinal axis of
device 130, corresponding to a desired lesion. The opening would be
controllably directed toward target tissue 10, as discussed above,
to create an intermediate lesion. Additionally, steering system 102
may be constructed as to limit the deflection of intermediate
portion 118 to one plane, ensuring, for example, that the opening
of the cryo-based ablation device 130, discussed immediately above,
is directed toward target tissue 10.
[0081] While the ablative device 130 is preferably adapted to emit
microwave energy sufficient to ablate the target tissue upon which
a lesion is desired, other ablative energies utilized by an
ablative device 130 in catheter 100 may include, but is not limited
to, one or more of the following energies, along or in combination:
microwave energy, laser energy or other forms of light energy in
both the visible and nonvisible range, radio frequency (RF) energy,
ultrasonic energy, cryogenic energy, chemical agent, thermal
energy, or any other energy which can be controllably emitted and
directed at least towards a portion of a desired target tissue,
transporting ablation energy to the target tissue at sufficient
energy levels resulting in tissue ablation and corresponding lesion
formation.
[0082] One exemplary ablation device 130 comprises a monopole
microwave antenna as disclosed and further described in commonly
owned U.S. Pat. No. 6,277,113, entitled "Monopole Tip for Ablation
Catheter and Methods for Using Same," which is hereby incorporated
herein by reference, in its entirety. Alternatively, ablation
device 130 may comprise other microwave antenna structures as
disclosed and further described in commonly owned U.S. Pat. No.
6,245,062, entitled "Directional Reflector Shield Assembly for a
Microwave Ablation Instrument," U.S. patent application Ser. No.
09/484,548, filed Jan. 18, 2000, entitled "Microwave Ablation
Instrument With Flexible Antenna Assembly and Method", and U.S.
patent application Ser. No. 09/751,472, filed Dec. 28, 2000,
entitled "A Tissue Ablation Apparatus with a Sliding Ablation
Instrument and Method," all hereby incorporated herein by
reference, each in its entirety.
[0083] Additionally, catheter 100 may further comprise one or more
electrodes strategically placed upon the distal portion 124 to
facilitate capture of certain electrophysiological signals. Such
signals allow a User to determine tissue characteristics of a
target tissue site and also provide confirmation that the distal
portion 124 is properly positioned substantially proximal and
parallel to a target tissue, for example. Such electrode
arrangement systems may be similar to those disclosed in U.S.
patent application Ser. No. 09/548,331, filed Apr. 12, 2000,
entitled "Electrode Arrangement for Use in A Medical Instrument,"
hereby incorporated herein by reference, in its entirety.
[0084] While the present invention has been primarily described
with respect to tissue ablations within the right atrium of the
heart, it will be appreciated that the ablation systems disclosed
herein may just as easily be applied to ablation of other tissues,
such as the tissue surrounding the sinus cavities for example. The
tissue ablations may be performed through either open surgery
techniques or through minimal invasive techniques.
[0085] Although the foregoing invention has been described in some
detail for purposes of clarity of understanding, it will be
apparent that certain changes and modifications may be practiced
within the scope of the appended claims.
* * * * *